Princeton's WordNet

1. underscore, underline(verb)

   a line drawn underneath (especially under written matter)

2. underscore, underline, emphasize, emphasise(verb)

   give extra weight to (a communication)

   "Her gesture emphasized her words"

3. underline, underscore(verb)

   draw a line or lines underneath to call attention to

Kernerman English Learner's Dictionary

1. underline(verb)ˈʌn dərˌlaɪn

   to make a line under a line of writing

   Underline the date and title.

2. underlineˈʌn dərˌlaɪn

   to make sth more obvious; = emphasize

   a crisis that underlines the need for change

Wiktionary

1. underline(Noun)

   A line placed underneath a piece of text in order to provide emphasis or to indicate that it should be viewed in italics or that it acts as a hyperlink

2. underline(Noun)

   An character

3. underline(Verb)

   To draw a line underneath something, especially to add emphasis; to underscore

4. underline(Verb)

   To emphasise or stress something

5. underline(Verb)

   To influence secretly.

   By mere chance in appearance, though underlined with a providence, they had a full light of the infanta. uE000100723uE001 Sir H. Wotton.

6. underline(Adjective)

   Passing under a railway line.

Origin: under + line

Webster Dictionary

1. Underline(verb)

   to mark a line below, as words; to underscore

2. Underline(verb)

   to influence secretly

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